urltools for Everyone

#1445 is great, if you use node.  For those that don't this should mean we can find a reasonable fallback.
Users can force urltools to use a specific system by setting `URLTOOLS_METHOD` to one of:
* `node`
* `python`
* `ruby`
* `php`
* `perl`

Note that you can't (currently) choose which `perl` sublibrary to use, it will use either `URI::Encode`, `URI::Escape`, or regular expressions in that order of preference.

plugins/urltools/urltools.plugin.zsh

@@ -4,6 +4,33 @@
 # Taken from:
 # http://ruslanspivak.com/2010/06/02/urlencode-and-urldecode-from-a-command-line/
 
-alias urlencode='node -e "console.log(encodeURIComponent(process.argv[1]))"'
+if [[ $(whence $URLTOOLS_METHOD) = "" ]]; then
+    URLTOOLS_METHOD=""
+fi
 
-alias urldecode='node -e "console.log(decodeURIComponent(process.argv[1]))"'
+if [[ $(whence node) != "" && ( "x$URLTOOLS_METHOD" = "x"  || "x$URLTOOLS_METHOD" = "xnode" ) ]]; then
+    alias urlencode='node -e "console.log(encodeURIComponent(process.argv[1]))"'
+    alias urldecode='node -e "console.log(decodeURIComponent(process.argv[1]))"'
+elif [[ $(whence python) != "" && ( "x$URLTOOLS_METHOD" = "x" || "x$URLTOOLS_METHOD" = "xpython" ) ]]; then
+    alias urlencode='python -c "import sys, urllib as ul; print ul.quote_plus(sys.argv[1])"'
+    alias urldecode='python -c "import sys, urllib as ul; print ul.unquote_plus(sys.argv[1])"'
+elif [[ $(whence ruby) != "" && ( "x$URLTOOLS_METHOD" = "x" || "x$URLTOOLS_METHOD" = "xruby" ) ]]; then
+    alias urlencode='ruby -r cgi -e "puts CGI.escape(ARGV[0])"'
+    alias urldecode='ruby -r cgi -e "puts CGI.unescape(ARGV[0])"'
+elif [[ $(whence php) != "" && ( "x$URLTOOLS_METHOD" = "x" || "x$URLTOOLS_METHOD" = "xphp" ) ]]; then
+    alias urlencode='php -r "echo rawurlencode(\$argv[1]); echo \"\n\";"'
+    alias urldecode='php -r "echo rawurldecode(\$argv[1]); echo \"\\n\";"'
+elif [[ $(whence perl) != "" && ( "x$URLTOOLS_METHOD" = "x" || "x$URLTOOLS_METHOD" = "xperl" ) ]]; then
+    if perl -MURI::Encode -e 1&> /dev/null; then
+        alias urlencode='perl -MURI::Encode -ep "uri_encode($ARGV[0]);"'
+        alias urldecode='perl -MURI::Encode -ep "uri_decode($ARGV[0]);"'
+    elif perl -MURI::Escape -e 1 &> /dev/null; then
+        alias urlencode='perl -MURI::Escape -ep "uri_escape($ARGV[0]);"'
+        alias urldecode='perl -MURI::Escape -ep "uri_unescape($ARGV[0]);"'
+    else
+        alias urlencode="perl -e '\$new=\$ARGV[0]; \$new =~ s/([^A-Za-z0-9])/sprintf(\"%%%02X\", ord(\$1))/seg; print \"\$new\n\";'"
+        alias urldecode="perl -e '\$new=\$ARGV[0]; \$new =~ s/\%([A-Fa-f0-9]{2})/pack(\"C\", hex(\$1))/seg; print \"\$new\n\";'"
+    fi
+fi
+
+unset URLTOOLS_METHOD